Mercury-cathode chlorine cell and mercury feeding means



Sept. 3, 1968 HIROSHI SHIBATA 3,400,067

MERCURY-CATHODE CHLORINE CELL AND MERCURY FEEDINQ MEANS Filed March 11,1966 H FIG. I F- FIG. 2

INVEN TOR.

BY MM United States Patent 3,400,067 MERCURY-CATHODE CHLORINE CELL ANDMERCURY FEEDING MEANS Hiroshi Shibata, Nakoso-shi, Japan, assignor toKureha Kagaku Kogyo Kabushiki Kaisha, Tokyo-to, Japan Filed Mar. 11,1966, Ser. No. 533,585 Claims priority, application Japan, Mar. 18,1965, 40/ 15,796 3 Claims. (Cl. 204219) This invention relates toelectrolytic cells having mercury electrodes for electrolysis of alkalichloride solutions. More particularly, the invention relates to theconstruction of the inlet of a mercury-cathode chlorine cell having amercury inlet passage channel disposed perpendicularly to the flow ofthe mercury in the electrolytic chamber.

I have previously proposed a mercury-cathode chlorine cell for carryingout electrolysis by causing mercury to flow from and perpendicularly tothe longitudinal sides of a narrow electrolytic chamber as described inUS. patent application No. 450,755 of Apr. 26, 1965. This electrolyticcell in comparison with a conventional horizontal mercury-cathodechlorine cell has a wide mercury flow path width and a short mercuryflow path length and, in addition to being capable of accomplishinghighefiiciency electrolysis with high current densities, has advantagessuch as the need for only a small quantity of mercury.

In an electrolytic cell of this character, the mercury sent by a pumpfirst passes from the transverse direction of the electrolytic cellthrough a channel along the side in the longitudinal direction and thenenters the interior of the electrolytic cell. In this case, since theflow of the mercury passing through the channel is caused to undergo anabrupt right-angle change in direction at the point of its entrance intothe electrolytic cell, waves are formed at the flow surface and tend tocause breaks in the mercury flow.

It is an object of the present invention to provide improvement in theconstruction of the inlet of the electrolytic cell of the above statedcharacter whereby to render uniform the mercury flow from the inletpassage channel into the electrolytic chamber and, moreover, to preventwave motion in the flow surface in the electrolytic chamber.

According to the present invention there is provided a mercury-cathodechlorine cell of the character referred to above, characterized in thatthe mercury flowing from the mercury inlet channel is under a statichead pressure and is introduced into the electrolytic chamber through amercury flow guide slit comprising, in combination, a large number ofsmall holes formed through the bottom plate of the electrolytic chamberabove and in the direction of the inlet channel and a gap formed betweenthe bottom plate and a flow guide plate fixed parallell-y to the bottomplate and forming a ceiling covering the outlets of the small holes.

The nature, principle, and details of the invention will be more clearlyapparent from the following detailed description with respect topreferred embodiments of the invention as illustrated in theaccompanying drawings in which like parts are designated by likereference numerals.

In the drawings:

FIG. 1 is a simplified plan view showing one example of an electrolyticcell embodying the invention;

FIG. 2 is an elevational view in vertical section taken along the planeindicated by line II,,II in FIG. 1;

FIG. 3 is an elevational view in vertical section taken along the planeindicated by line IIIIII in FIG. 1;

3,400,067 Patented Sept. 3, 1968 FIGS. 4 and 5 are elevational views invertical section taken along planes equivalent to that indicated by lineIIIIII in FIG. 1, respectively showing other examples of theelectrolytic cell according to the invention; and

FIGS. 6(a), 6(b), and 6(0) are diagrammatic views respectively showingexamples of small holes suitable for use according to the invention.

Referring to FIGS. 1 through 3, the principal operational part of theelectrolytic cell shown is an electrolytic chamber 1 having a steelbottom plate 2 constituting a cathode. Along one side of theelectrolytic chamber 1 and below the bottom plate 2, there is provided amercury lower circuit channel 3, and numerous small through holes 4 areprovided in a row in the bottom plate 2 above the channel 3, the row ofholes extending over almost the entire length of the channel 3 andproviding communication from the channel 3 to the electrolyticchamber 1. The diameters of the holes 4 are increased progressively byslight increments toward the end of the chamber 1 on the side of IL, soas to produce almost equal mercury flow rate through all holes 4.

A mercury guide plate 5 is disposed to project inwardly from the sidewall of the electrolytic chamber 1 above the holes 4 with a gap 6 formedbetween the guide plate 5 and the upper surface of the bottom plate 2. Amercury outlet through 8 is provided along the side of the chamber 1opposite the side of the channel 3 and is connected at the outlet endthereof to an amalgam decomposer 9 or denuding tower. The mercuryrecovered from the amalgam decomposer 9 is recirculated by a mercurypump 10 by way of a mercury circuit side passage 11 connected to thechannel 3.

The mercury 7 which has been pumped by the pump 10 into the side passage11 is caused by static head pressure to flow through the mercury lowercircuit channel 3, from which the mercury passes through the holes 4 andemerges uniformly at the upper surface of the bottom plate 2. Here, themercury has a flow velocity in the vertical direction due to the headpressure but is thereafter caused by the guide plate 5 to change itsflow direction to that indicated by arrows and flows uniformly out fromthe gap 6.

That is, a How guide slit is formed by the holes 4 and the gap 6, andthe mercury flowing out of this flow guide slit already has a uniformvelocity in the same direction as the mercury flow in the electrolyticchamber. Accordingly, even when impurities such as graphite partides andmercury butter are produced within the electrolytic cell in the vicinityof the outlet of the flow guide slit, such impurities are immediatelyswept along with the mercury flow and discharged. Therefore, there is nopossibility of these impurities accumulating and lowering'the efficiencyof the electrolytic cell or of the generation of hydrogen within thecell.

As the mercury flows across the electrolytic chamber 1 to electrol-yzebrine, the amalgam thus formed is collected in the outlet through 8 anddenuded by the amalgam decomposer 9, and the resulting mercury is againcirculated by the pump 10 to the electrolytic cell.

In the above described electrolytic cell, it is possible also to omitthe mercury circuit side passage 11 and to force the mercury by pumppressure directly into the inlet circuit channel 3. Furthermore, thesmall holes 4 are not necessarily limited to circular holes but may becircular, elliptical, oblong, trapezoid, or of some other suitable shapeas indicated in FIG. 6-. Moreover, in some cases, these holes may bealigned in a plurality of rows.

The surface of the flow guide plate 5 directly contacting theelectrolyte is made of a chlorine-resistant, poor electrical conductorsuch as rubber, a synthetic resin, or a ceramic, but the lower surfaceto contact mercury is preferably a material such as iron which has highwettability with respect to mercury.

While the foregoing description relates toan example of an electrolyticcell wherein the electrolytic chamber, as a whole, is almost horizontal,the present invention can be applied also to a vertical typeelectrolytic cell in which the primary electrolytic chamber is almosthorizontal, and the secondary electrolytic chamber is inclined, asdescribed in US. patent application No. 450,755 of Apr. 26, 1965.Examples of electrolytic cells according to the invention each having ahorizontal electrolytic part and an inclined electrolytic part are shownin FIGS. 4 and 5.

The electrolytic cell of the above described construction andarrangement has the following effectiveness, utility, and advantages.According to the commonly held view in the prior art relative toelectrolytic cells of the instant type, the width of the mercury fiowfilm is limited to a maximum of approximately 3 metres and in most casesis from 0.8 to 1.5 metres, and, with any larger width, it has beenextremely difiicult to obtain a uniform mercury flow evenly over theentire flow film width.

I have found, however, that by causing the mercury under 'a static headpressure to be ejected through the small holes 4, which have a flowsmoothening and equalizing effect, and changing the flow of the mercurythus ejected into a uniform flow in the transverse direction by means ofa horizontal flow guide plate 5 as in the present invention, it ispossible to force the mercury to flow out evenly over the entire mercuryflow film width, which thereby 'may be increased to as much as 5 to 8metres.

Accordingly, in the design of high-current electrolytic cells, it is notnecessary to use an electrolytic chamber length of from 10 to 15 metresin the mercury flow direction, as in conventional practice, and it' ispossible to design an electrolytic cell of a length of only from 1 to 2metres in the mercury flow direction to produce the same performance.

This feature of the present invention means that the retention time (orpass through time) of the mercury within the electrolytic cell can beshortened and the amal-' garn concentration can be constantly sustainedat a low value, whereby the formation of mercury butter is diminished,and the small quantity of the mercury butter which may be formed ispromptly discharged out of the cell. Accordingly, almost no hydrogen isgenerated.

Furthermore, since the mercury is subjected to forced flow, ahigh-velocity, thin, and smooth flow of mercury can be achieved withalmost no inclination of the bottom plate of the electrolytic cell.Accordingly, the voltage regulation is facilitated, and it is possibleto carry out the electrolytic process with the voltage at a low value.

Moreover, an extremely shallow depth of the electrolytic chamber issufiicient, whereby the manufacturing cost of the electrolytic cell canbe lowered.

It is to be understood, of course, that the foregoing disclosure relatesto only preferred embodiments of the invention and that it is intendedto cover all changes and modifications of the examples of the inventionherein chosen for the purposes of the disclosure, which do notconstitute departures from the spirit and scope of the invention as setforth in the appended claims.

What I claim is:

1. In a mercury-cathode chlorine cell wherein mercury is caused to flowfrom a mercury circuit channel provided below an electrolytic chamberperpendicularly to the mercury flow direction along the bottom plate ofthe electrolytic chamber, through mercury flow guide means providedalong a side wall of the electrolytic chamber, and into the electrolyticchamber to flow horizontally or down a slight incline along the uppersurface of the bottom plate, mercury supply means to place the mercuryflowing from the mercury circuit channel under a static head pressureand a mercury flow guide slit constituting said mercury flow guidemeans, said cell being characterized in that said mercury flow guideslit comprises, in combination, a large number of small holes formedthrough the bottom plate of the electrolytic chamber above and in thedirection of the mercury circuit channel and a gap formed between thebottom plate of the electrolytic chamber and a flow guide plate fixedparallel to the bottom plate and forming a ceiling covering the outletsof said small holes.

2. A mercury cathode chlorine cell as claimed in claim 1, wherein therelative sizes, shapes, and spacing of the small holes of the mercuryflow guide slit are selected to produce a smooth mercury flow of uniformthickness across the entire width of mercury stream in the electrolyticchamber.

3. A mercury cathode chlorine cell as claimed in claim 1, wherein saidstatic head pressure of the mercury supply means is controllable.

References Cited UNITED STATES PATENTS 742,863 11/1903 Hannon 204-2191,055,504- 3/1913 Albrecht 204-275 XR FOREIGN PATENTS 1,376,105 9/1964France.

23,834 2/ 1901 Switzerland.

HOWARD S. WILLIAMS, Primary Examiner.

DONALD R. VALENTINE, Assistant Examiner.

1. IN A MERCURY-CATHODE CHLORINE CELL WHEREIN MERCURY IS CAUSED TO FLOWFROM A MERCURY CIRCUIT CHANNEL PROVIDED BELOW AN ELECTROLYTIC CHAMBERPERPENDICULARLY TO THE MERCURY FLOW DIRECTION ALONG THE BOTTOM PLATE OFTHE ELECTROLYTIC CHAMBER, THROUGH MERCURY FLOW GUIDE MEANS PROVIDEDALONG A SIDE WALL OF THE ELECTROLYTIC CHAMBER, AND INTO THE ELECTROLYTICCHAMBER TO FLOW HORIZONTALLY OR DOWN A SLIGHT INCLINE ALONG THE UPPERSURFACE OF THE BOTTOM PLATE, MERCURY SUPPLY MEANS TO PLACE THE MERCURYFLOWING FROM THE MERCURY CIRCUIT CHANNEL UNDER A STATIC HEAD PRESSUREAND A MERCURY FLOW GUIDE SLIT CONSTITUTING SAID MERCURY FLOW GUIDEMEANS, SAID CELL BEING CHARACTERIZED IN THAT SAID MERCURY FLOW GUIDESLIT COMPRISES, IN COMBINATION, A LARGE NUMBER OF SMALL HOLES FORMEDTHROUGH THE BOTTOM PLATE OF THE ELECTROLYTIC CHAMBER ABOVE AND IN THEDIRECTION OF THE MERCURY CIRCUIT CHANNEL AND A GAP FORMED BETWEEN THEBOTTOM PLATE OF THE ELECTROLYTIC CHAMBER AND A FLOW GUIDE PLATE FIXEDPARALLEL TO THE BOTTOM PLATE AND FORMING A CEILING COVERING THE OUTLETSOF SAID SMALL HOLES.